I n t e r n a t i o n a l
T e l e c o m m u n i c a t i o n
ITU-T
TELECOMMUNICATION
STANDARDIZATION SECTOR
OF ITU
U n i o n
Technical Paper
(25 October 2019)
TP-TEST-UE-MS
Guideline for general test procedure and
specification for measurements of the LTE,
3G/2G user equipment/mobile stations (UE/MS)
for over-the-air performance testing
Summary
Typical conformance tests include transmitter maximum output power, spectrum emission mask,
spurious emissions, minimum output power, and adjacent channel leakage power ratio as well as
receiver adjacent channel selectivity, blocking characteristics, spurious response, intermodulation
characteristics, spurious emissions, and reference sensitivity level.
This Technical Paper gives an analysis of the work in relevant standards development organisations
(SDOs) and a survey of the requirements, and then describes a common testing methodology for LTE,
3G/2G user equipment/mobile stations (UE/MS) for over-the air (OTA) performance testing.
Keywords
Antenna, over-the-air, OTA, performance testing, LTE, 3G/2G, user equipment, UE, mobile stations,
MS.
Change Log
This document contains Version 1 of the ITU-T Technical Paper on “Guideline for general test
procedure and specification for measurements of the LTE, 3G/2G user equipment/mobile stations
(UE/MS) for over-the-air performance testing” approved at the ITU-T Study Group 11 meeting held
in Geneva, 16-25 October 2019.
Editor:
Awad Ahmed Ali Hmed Mulah
NTC
Sudan
E-mail: awadmulah@ntc.gov.sd
Editor:
Uwe Baeder
Rohde & Schwarz
Germany
E-mail: Uwe.Baeder@rohde-schwarz.com
Editor:
Alexander Nähring
Rohde & Schwarz
Germany
E-mail: Alexander.Naehring@rohde-schwarz.com
ii
TP-TEST-UE-MS (2019)
Table of Contents
Page
1
Scope............................................................................................................................. 1
2
References..................................................................................................................... 1
3
Definitions .................................................................................................................... 1
4
Abbreviations and acronyms ........................................................................................ 1
5
Conventions .................................................................................................................. 2
6
Survey and analysis of existing work in the relevant SDOs ......................................... 2
6.1
3GPP (3rd Generation Partnership Program) ................................................. 2
6.2
CTIA – The Wireless Association .................................................................. 3
6.3
ETSI (European Standardisation Institute) ..................................................... 3
6.4
CCSA (China Communications Standards Association) ............................... 3
6.5
Conclusion of the survey ................................................................................ 3
7
General description ....................................................................................................... 3
7.1
Test procedure ................................................................................................ 3
7.2
Coordinate system .......................................................................................... 3
7.3
Test site characteristics and validation ........................................................... 4
7.4
Test site calibration......................................................................................... 5
8
Measurement frequencies ............................................................................................. 6
9
Transmitter performance .............................................................................................. 6
10
Receiver performance ................................................................................................... 7
11
Positioning requirements and phantoms ....................................................................... 7
12
Measurement sites ........................................................................................................ 8
Bibliography............................................................................................................................. 10
TP-TEST-UE-MS (2019)
iii
Technical Paper ITU-T TP-TEST-UE-MS
ITU-T Technical Paper
Guideline for general test procedure and specification for measurements
of the LTE, 3G/2G user equipment/mobile stations (UE/MS)
for over-the-air performance testing
1
Scope
This document describes a common testing methodology for requirements that are usually divided in
two major aspects, one for the transmitter and one for the receiver as in the following examples:
–
–
Transmitter output power (as total radiated power (TRP));
Receiver sensitivity level (as total radiated sensitivity (TRS) or total isotropic sensitivity
(TIS)).
The test procedure described in this document measures the performance of the transmitter and the
receiver.
2
References
None.
3
Definitions
None.
4
Abbreviations and acronyms
This Technical Paper uses the following abbreviations and acronyms:
BER
Bit Error Ratio
DUT
Device Under Test
EIRP
Equivalent Isotropically Radiated Power
EIS
Effective Isotropic Sensitivity
E-UTRA
Evolved UMTS Terrestrial Radio Access
E-UTRAN Evolved UMTS Terrestrial Radio Access Network
FER
Frame Error Rate
FSPL
Free-Space Path Loss
LTE
Long Term Evolution
NR
New Radio
RF
Radio Frequency
TRP
Total Radiated Power
TRS
Total Radiated Sensitivity
TIS
Total Isotropic Sensitivity
MS
Mobile Station
TP-TEST-UE-MS (2019)
1
OTA
Over The Air
QZ
Quiet Zone
RED
Radio Equipment Directive
SDO
Standards Development Organization
UE
User Equipment
UTRA UMTS Terrestrial Radio Access
5
Conventions
None.
6
Survey and analysis of existing work in the relevant SDOs
This clause presents the work of major standardization organisations. However, there is no claim for
completeness. In addition to the definition of test limits, all published material gives a very detailed
and exact definition of the test and measurement environment. Meaningful requirements with
minimized measurement uncertainty and a high guaranteed reproducibility are a basic need for
making a test definition authoritative for validation and certification purpose.
6.1
3GPP (3rd Generation Partnership Program)
In 3GPP extensive work has been done to produce specifications for methods procedures and
requirements for over the air (OTA) antenna tests [b-3GPP]. Table 1 provides a list of the
specifications and their purposes.
Table 1 – 3GPP specifications for methods procedures and requirements for OTA
Specification or
Report
Title
Description
TS 34.114
User Equipment (UE) / Mobile
Station (MS) Over The Air (OTA)
antenna performance; Conformance
testing
Describes the test procedure for the radiated
performances measurements of the 3G/2G
user equipment/mobile stations (UE/MS) in
active mode in both the uplink and the
downlink, total radiated power (TRP) and
total radiated sensitivity (TRS).
TS 37.144
User Equipment (UE) and Mobile
Station (MS) GSM, UTRA and
E-UTRA over the air performance
requirements
Document to establish over the air antenna
minimum requirements for user equipment
(UE) and mobile station (MS).
TS 37.544
User Equipment (UE) Over The Air
(OTA) performance;
Conformance testing
Describes the test procedure for the radiated
performances measurements of the user
equipment (UE) UMTS/LTE for TRS/TIS
with the extension of multiple receive
antennas. Definition of recommended
performance values.
Current work in 3GPP also includes the OTA measurements for new radio (NR) for cm- and
mm-wave frequencies as well as OTA MIMO testing. NR is planned as a candidate submission to
IMT-2020. The 3GPP standards define the details of the measurement procedure and the test
environment.
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6.2
CTIA – The Wireless Association
CTIA has developed a comprehensive test plan for OTA performance requirements [b-CTIA]) that
covers GSM, UMTS and LTE as well as other cellular and non-cellular standards. Test procedures
for single and diversity receiver devices are described. From the requirements side only North
American bands, hence ITU Region 2 are covered.
6.3
ETSI (European Standardisation Institute)
With the introduction of the radio equipment directive (RED) the market approval requires
certification of UEs/MS to comply with OTA requirements. ETSI is now developing a harmonised
standard taking care of TRP and TRS procedures and requirements as a revision of EN 301 908-2
(3G), EN 301 908-13 (LTE) and EN 301 908-25 (NR). It is very likely that procedures are following
the approach as described in the 3GPP documents mentioned in clause 6.1. It is expected that
requirements are also taken from 3GPP for bands and technologies that are present. Missing values
are added in the process of the creation of the harmonised standard. For EN-301 908-2, the final draft
is ready for the approval stage [b-ETSI], with planned approval in February 2020 and publishing in
January 2021. This activity will of course focus on bands for region 1.
6.4
CCSA (China Communications Standards Association)
CCSA developed a series of standards for radiated performance including 2G/3G and LTE
Technology YD/T 1484 "Measurement method for radiated RF power and receiver performance of
wireless device" [b-CCSA]. The measurement procedures mainly follow the approach as described
in the 3GPP documents.
6.5
Conclusion of the survey
It can be concluded that there is extensive material available in this field. The following clauses will
introduce the underlying principles and common considerations. This material may therefore serve
as an assistance and guideline to evaluate and introduce general test procedures and specifications for
measurements of the LTE, 3G/2G user equipment/mobile stations (UE/MS) for over-the-air
performance testing.
7
General description
7.1
Test procedure
The test procedure for OTA testing is separated in three steps:
1.
The test chamber set-up and performance evaluation;
2.
The path loss measurement of the test system for calibration;
3.
The performance measurement of the device under test (DUT).
7.2
Coordinate system
The definition of TRP and TIS measurements are based on a spherical coordinate system as described
in clause 3.4 of [b-CTIA]. The spherical coordinate system describes any point in 3D space relative
to the coordinate system origin with three spherical coordinates (𝑟, 𝜃, 𝜙). A point on a sphere with
radius 𝑟 around the origin is described with (𝜃, 𝜙), with elevation 𝜃 ∈ (0°, 180°) and azimuth 𝜙 ∈
(0°, 360°). The equator is located at 𝜃 = 90° elevation. For OTA measurements, the convention ISO
80000-2:2009 for spherical coordinates is used. In a Cartesian coordinate system, the x-axis points
towards 𝜃 = 90°, 𝜙 = 0°, the y-axis points towards 𝜃 = 90°, 𝜙 = 90°, and the z-axis towards 𝜃 =
0°. For measurements, the DUT is located in the coordinate system origin and the measurement
TP-TEST-UE-MS (2019)
3
antenna is located in direction (𝜃, 𝜙) relative to the DUT. As the path loss caused by the distance
between DUT and measurement antenna must be calibrated for the test system, the radius 𝑟 is not
required.
Figure 1 – Spherical coordinate system, in line with [b-IEEE]
At each measurement point, two orthogonal components of the field are measured, defined as the
theta polarization 𝐸⃗𝜃 and phi polarization 𝐸⃗𝜙 , pointing along the corresponding rotation vectors 𝜃 and
𝜙, respectively. The theta polarization vector points along the positive direction of increasing theta
values, and the phi polarization vector points along the positive direction of increasing phi values.
7.3
Test site characteristics and validation
For a measurement site to qualify for performance testing of a DUT, the measurement site must
provide a sufficient quiet zone (QZ) performance, effective shielding and accurate positioning.
The minimum measurement distance 𝑅 is determined by the far field condition. The distance between
DUT and the measurement antenna must fulfil:
2𝐷2
𝑅 ≥ max (
, 3𝐷, 3𝜆)
𝜆
where 𝐷 is the maximum extension of the radiator (DUT).
The three inequalities represent different minimum distances to fulfil uncertainty limits. The
Fraunhofer distance 𝑅 ≥ 2𝐷2 /𝜆 fulfils the phase uncertainty and is the far field distance for
electrically large antennas. 𝑅 > 3𝐷 fulfils the amplitude uncertainty limit and 𝑅 > 3𝜆 the near field
limit. In [b-CTIA], the radiator dimension is fixed to 300 𝑚𝑚 for all handhelds with phantoms. Here,
the largest “minimum measurement distance” required for CTIA testing of 2G, 3G and 4G frequency
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TP-TEST-UE-MS (2019)
bands is 1.61 𝑚, resulting from a maximum frequency of 2690 𝑀𝐻𝑧 in the high channel of 3GPP
Band 41. If a measurement system uses smaller distances other than defined by the minimum
measurement distance equation, the validity of the measurement results must be demonstrated to the
standardization body beforehand.
The QZ of the measurement site is qualified using a QZ ripple test. It is used to characterize variations
in the field measurement caused by reflections within the anechoic chamber. Phi and theta cuts of
highly symmetrical dipole or loop antennas are measured at different locations in the QZ. Deviations
of the pattern cuts from a perfect circle are attributed to amplitude ripples in the quiet zone caused by
imperfections of the measurement site.
7.4
Test site calibration
The test system losses including the free-space path loss (FSPL) must be compensated. For this, a
calibration of the system is performed. A method to determine the system losses is the reference
antenna method or gain transfer method. With this, a reference measurement is performed for each
signal path. The reference measurement and known gain of the reference antenna determine the
system loss of the current signal path. For each signal path used for UE performance measurements,
up-to-date correction data must be available for correct assessment of equivalent isotropically
radiated power (EIRP) and effective isotropic sensitivity (EIS) and consequently determination of
TRP and TIS. The number of signal paths depends on the used system. Typically, at least two signal
paths for the two polarization components 𝐸⃗𝜃 and 𝐸⃗𝜙 are required. Additional signal paths may be
required for additional probe antennas, frequency ranges or test instrument set-ups.
Figure 2 – Illustration of test site calibration set-up
To determine the correction value for a given signal path 𝐿sig-path, a reference antenna with known
gain 𝐺𝑟𝑒𝑓 is placed in the rotation centre, polarization matched with the probe antenna and the peak
gain direction aligned to the probe antenna. The signal path loss 𝐿sig-path is measured. This can be
done with an auxiliary cable with known transmission parameters used to connect a signal generator
and signal analyser to the system as shown in Figure 2. Alternatively, a reference receiver can be
connected to the reference antenna and a signal with known power is fed to the signal path. Best
practice for minimizing uncertainty is to use the same instrument for calibration and measurement
when applicable. The auxiliary cable is not used during DUT performance testing and individual
calibrations may be used for transmitter and receiver tests, using the spectrum analyser and signal
generator connected to the signal path cable, respectively.
TP-TEST-UE-MS (2019)
5
When measuring the receiver power 𝑃𝑅𝑋 with known transmit power 𝑃𝑇𝑋 , antenna gain 𝐺𝑟𝑒𝑓 , and
auxiliary cable loss 𝐿𝑎𝑢𝑥 , the signal path loss 𝐿sig-path = 𝐹𝑆𝑃𝐿 − 𝐺𝑝𝑟𝑜𝑏𝑒 + 𝐿𝑝𝑎𝑡ℎ can be
straightforwardly determined:
𝐿sig-path = 𝑃𝑇𝑋 − 𝑃𝑅𝑋 − 𝐿aux + 𝐺𝑟𝑒𝑓
For every change on the measurement set-up, used connections, cables, adapter, switches, etc., the
correction must be determined anew. In case of non-linearity of used components, the calibration
must also be performed for various power levels and must be applied correctly during measurement.
8
Measurement frequencies
The radiation patterns of handset antennas can be expected to be frequency dependent. Achieved TRP
and TRS values can vary over frequency and shall be measured in three channels in a frequency band
(low, mid and high channel). The specified bands will be chosen to cover national or regional aspects.
Tables of the frequency bands designated for the different wireless communication standard can be
found in the respective standard documents. For any DUT, frequencies are selected based on the
supported frequency bands of all supported wireless communication standards of the device and the
admitted frequencies in the region the DUT is to be operated.
9
Transmitter performance
This clause specifies the test method and test requirements for the radiated power measurement.
The radio frequency (RF) transmitter performance is qualified by sampling the radiated transmit
power on a sphere around the DUT. The DUT is placed in a holding fixture on the positioning system
in the QZ centre, combined with phantoms as further explained in clause 11.
The measurement site is expected to be validated and calibrated as defined in clause 7 and the power
radiated by the DUT shall be measured with a calibrated measurement instrument such as spectrum
analyser, power meter or other measurement receiver.
The signal power as received by the measurement receiver test instrument is corrected by the
corresponding signal path correction of the currently active signal path as determined during
calibration. The resulting value is the EIRP of the current polarization in the current measurement
direction. To access the total radiated power of the DUT, the EIRP in all direction is spatially
averaged:
𝑇𝑅𝑃 =
1 2𝜋 2𝜋
∫ ∫ 𝐸𝐼𝑅𝑃(𝜃, 𝜙) ⋅ sin(𝜃) 𝑑𝜃 𝑑𝜙
4𝜋 0 0
As the 𝐸𝐼𝑅𝑃 is measured as vertical and horizontal component with a dual polarized probe antenna
at sampled measurement locations, the TRP is approximated with:
𝑁−1 𝑀−1
𝜋
𝑇𝑅𝑃 ≈
∑ ∑ (𝐸𝐼𝑅𝑃𝜃 (𝜃𝑛 , 𝜙𝑚 ) + 𝐸𝐼𝑅𝑃𝜙 (𝜃𝑛 , 𝜙𝑚 )) sin(𝜃𝑛 )
2𝑁𝑀
𝑛=0 𝑚=0
The measurement locations (𝜃𝑛 , 𝜙𝑚 ) are defined in a grid on a sphere around the DUT. The angular
spacing of measurement points is chosen as a trade-off between measurement time and accuracy,
while for low directivity antennas as used in typical UE for 2G, 3G, and 4G a low sampling of 15° is
sufficient.
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10
Receiver performance
The RF receiver performance is qualified by sampling the minimum effective isotropic sensitivity on
a sphere around the DUT. The DUT is placed in a holding fixture on the positioning system in the
QZ centre, combined with phantoms as further explained in clause 11.
The measurement site is expected to be validated and calibrated as defined in clause 7 and the signal
received by the DUT shall be transmitted with a calibrated test instrument. To access the EIS of the
receiver in a given direction, the transmitted signal is reduced in power until the error criteria (e.g.,
bit error ratio (BER) or frame error rate (FER)) is above a defined threshold. The lowest signal power
that still enables the receiver to be within the error criteria limits, corrected by the corresponding
signal path correction of the currently active signal path, is the EIS of the receiver for the given
direction and polarization.
The total isotropic sensitivity (TIS) is the EIS spatially averaged over the whole sphere around the
DUT:
𝑇𝐼𝑆 =
4𝜋
2𝜋 𝜋
1
1
+
) 𝑠𝑖𝑛𝜃𝑑𝜃 𝑑𝜙
∫0 ∫0 (
𝐸𝐼𝑆𝜃 (𝜃, 𝜙) 𝐸𝐼𝑆𝜙 (𝜃, 𝜙)
It is important to note, that for TIS determination, it is not sufficient to rely on the conducted
sensitivity of the receiver combined with the radiation pattern of the used antenna, as signal strength
and noise received by the antenna will vary and is influenced by the DUT itself.
To determine the TIS from sampled measurement points, the TIS is approximated with:
𝑇𝐼𝑆 ≈
2𝑁𝑀
1
1
𝑀−1
𝜋 ∑𝑁−1
+
) sin(𝜃𝑖 )
𝑖=1 ∑𝑗=0 (
𝐸𝐼𝑆𝜃 (𝜃𝑖 , 𝜙𝑗 ) 𝐸𝐼𝑆𝜙 (𝜃𝑖 , 𝜙𝑗 )
where 𝐸𝐼𝑆𝜃 (𝜃𝑖 , 𝜙𝑗 ) and 𝐸𝐼𝑆𝜙 (𝜃𝑖 , 𝜙𝑗 ) are the determined effective isotropic sensitivity in the
direction (𝜃𝑖 , 𝜙𝑗 ) in the theta and phi polarization, respectively.
The measurement locations (𝜃𝑛 , 𝜙𝑚 ) are defined in a grid, e.g., 15° on a sphere around the DUT, as
defined for transmitter performance in clause 9.
11
Positioning requirements and phantoms
The surveyed standardization bodies determine positioning requirements including the use of holding
the DUT in different configurations with phantom heads and hands. Test cases describe well defined
UE positioning for test comparability and the use of phantoms to mimic real life use of the UE.
Typically, UEs are classified by their form factor (size, shape) and typical usage scenario (voice, data,
wrist). These positions include free space (FS), head and hand phantom left and right (BHHL,
BHHR), hand phantom left and right (HL, HR), and wrist-worn left and right (WL, WR) (see Figure
3). Due to the influence of the phantoms on the DUT performance, both the DUT and phantom must
fit inside the QZ of the test system. The test system must be able to hold the full configuration and
fix it to an accurate location while the whole fixture is rotated by the positioning system. It should be
noted that [b-CTIA] currently only defined phantoms for UE up to 92 mm device width, with a fixed
QZ size of 300 mm.
TP-TEST-UE-MS (2019)
7
Figure 3 – Head and hand phantom in anechoic chamber
12
Measurement sites
Figure 4 illustrates a combined axis positioning system and a distributed axis positioning system for
measurement sites.
Figure 4 – Combined axis positioning system (left) and distributed axis
positioning system (right)
The measurement site must fulfil the positioning and QZ requirements as defined in clauses 7 and 11.
The set-up must be able to position DUT and probe antenna so that the required measurement
locations can be reached in 3D space. The minimum distance must be fulfilled or an alternative
methodology be used that retrieves results that are equal to values obtained in far field. The default
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TP-TEST-UE-MS (2019)
set-up is an anechoic chamber with an automated 3D positioning system. The two major positioner
systems are the combined axis and distributed axis positioner systems. The coordinate systems for
both set-ups differ in orientation but are physically identical and the generic spherical coordinate
system defined in clause 7 applies to both. Figure 4 shows a schematic overview of the two
positioning system layouts in an anechoic chamber. Figure 5 shows a real life anechoic chamber with
a distributed axis positioning system.
Figure 5 – Anechoic chamber with distributed axis positioning system
TP-TEST-UE-MS (2019)
9
Bibliography
[b-3GPP]
3GPP, The Mobile Broadband Standard <https://www.3gpp.org>
[b-CCSA] China Communications Standards Association, <www.ccsa.org.cn>
[b-CTIA]
CTIA, Test Plan for Wireless Device Over-the-Air Performance, version 3.8.1, October
2018. <https://api.ctia.org/wp-content/uploads/2018/10/ctia-test-plan-for-wirelesss-device-over-the-air-performancever-3-8-1.pdf>
[b-ETSI]
<https://portal.etsi.org/webapp/WorkProgram/Report_WorkItem.asp?WKI_ID=50586>
[b-IEEE]
IEEE Std. 149-1979 <https://ieeexplore.ieee.org/document/19510>
__________________
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